QUESTION 19 The gure shows a lens made of glass with index of refraction equal to 133' The curvature radius of its front surface is 0957 m in magnitude, and that of its back surface is 0392 In in magnitude What is the focal length of the lens (in in; answer sign and magnitude)? Front QUESTION 20 You are designing a symmetric double convex lens that is made of glass with index of refraction equal to 1.33 and has a focal length of +0.16l m. What curvature radius of the lens surface should you use (in in; answer a positive number)? 0 Double convex